<!DOCTYPE html>
<html lang="en">
<head>
    <meta charset="UTF-8">
    <meta name="viewport" content="width=device-width, initial-scale=1.0">
    <title>Document</title>
</head>
<body>
    <script>
        var names = 'asdoWasWCi'
        //toLowerCase把字符串全部转化为小写;返回一个新字符串
        //toUpperCase把字符串全部转化为大写;返回一个新字符串
        console.log(names.toLowerCase());
        console.log(names.toUpperCase());
        //不会改变原字符串
    </script>
</body>
</html>